The present invention relates to ink jet printers using thermally fusible ink. One such ink jet printer comprises an ink nozzle defining a feed passage for feeding the thermally fusible ink and an orifice for ejecting the ink, heating means for heating and fusing the ink, ejection drive means for ejecting the fused ink from the orifice, and ejection control means for operating the ejection drive means in accordance with an image signal.
This printer is capable of using high density ink to realize prints of excellent tone quality since the ink acting as an image recording medium is heated and fused for ejection. Color toners and various types of ink intended for use in electrophotographic copying machines and various printers of the thermal sublimation type may also be used in this type of ink jet printer.
One example of such ink jet printers is disclosed in Japanese Patent Publication Kokai No. 61 137168. This printer comprises a holder with a nozzle orifice for holding solid conductive ink (carbon ink), and an electrode disposed between the holder and recording paper. A high voltage is applied to the electrode and the solid conductive ink to generate sparks therebetween (arc discharge), thereby to fuse a leading part of the ink and to eject the fused ink from the orifice to the recording paper.
Such an ink jet printer, however, has the following disadvantages:
The ejection drive means for applying a high, spark producing voltage to the electrode and the solid conductive ink to impart a drive for ejecting the fused ink from the orifice, acts also as heating means for fusing a leading part of the solid conductive ink. The drive and heating means having the two functions contributes toward a simplified construction. However, the fusion of the solid conductive ink relies on the energy imparted by the sparks, and the amount of energy is variable under the influences of ambient electric fields, electric capacity of recording paper, surrounding atmosphere (temperature and humidity) and so forth. As a result, there occur variations in the amount of ink fused and ejected by one spark, which tend to deteriorate the quality of recorded images. Because of this fact and the very high drive voltage required to generate sparks for fusing and ejecting the solid conductive ink, it has been difficult to achieve high speed recording by employing line printing.
This printer has the further disadvantage that the range of usable ink is limited to conductive ink. There has been a poor prospect for this type of printer being adapted for color printing since the commercial availability of conductive color ink is limited.